1. Field of the Invention
The present invention relates generally to an interactive television system (iTVsystem) that renders on-demand interactive multimedia services for a community of users. More particularly, the invention relates to a system architecture that comprises an improved multimedia-capable network architecture, which consists of a series of multiple building blocks and multiple intercommunication links that connect all the building blocks together.
In a preferred embodiment, the system uses a workgroup computer. It contains an on-demand workgroup server and 4 workgrouped Channel-processors and the fastest peer-to-peer workgroup connectivity on an internal workgroup link. It provides not only the multimedia on-demand service for the 4 workgrouped Channel-processors from the workgroup server but also the fastest communication among these 4 Channel-processors through the internal workgroup link. The workgroup computer is an important building block for constructing a multimedia-capable network. It creates a better multimedia network architecture where the intensive workgroup on-demand sharing will not generate unnecessary network traffic to hamper the already congested network communication. Most importantly, it will not in any way affect other workgroups' concurrent on-demand sharing activities.
Therefore, every client Channel-processor on the LAN can provide the multimedia on-demand services, and at the same time, interface with LAN servers for other non-on-demand non-time-critical services.
The system uses a set-top-box called iTVpanel. Typically, it contains a keyboard interface, a serial-port interface, a data/control link to its host workgrouped Channel-processor, a video input for CATV RF signal, and an NTSC/PAL output to the television. The user can use this set-top-box to control any one of the Channel-processors that render the interactive TV services whenever he/she wants it.
The system utilizes the Channel-processor to create the "private-viewing" interactive TV channel and the iTV server, which is an iTV application-oriented LAN server, to create a "group-viewing" interactive TV channel. On a private-viewing channel, the user can order any on-demand services for movies, games and shopping. On a group-viewing channel, the user can interact with a number of group-based games, shopping activities and forums. The system can also accommodate the regular CATV channels or Pay-per-view channels, which can be classified as non-interactive "public-viewing channels".
The size of the total population that can be serviced by the system is based on how many interactive TV channels are to be implemented. On an analog carrier for video delivery using RG59 RF cable or microware, the system can create up to 150 channels to serve a group of 1,000 users. On a digital carrier using ATM/Fiber or the like, the system will provide the interactive TV services for a whole community.
2. Prior Art
The merging of computer technology and various forms of entertaining and informational media provides a natural base for interactive multimedia involving a community of users. Such a community of users may, for example, include guests in respective rooms of a hotel. A preferred form of the interactive television system that delivers interactive multimedia on a TV should provide private-viewing interactive TV services, so that the user can order at any time the on-demand services for movies, games and shopping. It should also provide the group-viewing interactive TV services, so that the user can interact with a number of group-based games, shopping activities and forums. From a business standpoint, the preferred iTV system should be easy and relatively inexpensive to install, compatible with existing Cable TV or Air TV services and sufficiently flexible to accommodate a small number of users (i.e., 32) up to a large number of users (i.e., 8,000). Moreover, such systems should cascade themselves easily through the common digital backbone, so that the number of users can be increased without any limitation.
Currently, the iTV service can be rendered based on a "two-layer single-link" client-server network architecture, which consists of a series of client computers and LAN servers, and a single internal network link that connects them all together. In order to provide iTV service to a community of users, the current execution requires use of a costly client computer to be powerful enough to receive the multimedia data stream, generate digital video to display on a TV, and at the same time interface with the user. Also, it requires to implement a costly broader-bandwidth network link to accommodate all the unregulated traffic, such as the client-to-server traffic for the interactivity, the server-to-client traffic for the video delivery and the server-to-server traffic for data exchange. In addition, it requires to use a very powerful LAN server to provide the concurrent multimedia on-demand sharing for all the client computers. But, in reality, the LAN server can never be stable enough to sustain the concurrent multimedia on-demand sharing for all the client computers. Furthermore, it can be proven that LAN servers are simply not ideal for providing the concurrent multimedia on-demand sharing. That is to say, the on-demand multimedia LAN servers are neither technically-feasible nor economically practicable.
Generally speaking, non-multimedia data, such as text-only data, are more likely to be small-volume and short-streamed, while multimedia data, such as digital-audio and digital-video data, are more likely to be large-volume and long-streamed. For example, to generate a one-minute video on a screen, a computer has to constantly retrieve and process the multimedia data from a local CD-ROM, a local hard disk or a LAN server for one minute without stopping.
In order to process the digital multimedia data stream, a double-speed CD-ROM drive, which generates 300 KB/sec throughput, meets the basic requirement to run an MPEG-I digital video (1.5-3 Mbits/sec), so the full-motion full-screen audio/video can then be properly processed and displayed on the monitor. If using MPEG-II (3-6 Mbits/sec), then the throughput requirement is at least 500-600 KB/sec, which is equivalent to what a quad-speed CD-ROM drive can provide.
At present, a hard disk can only provide the maximum random seek throughput at about 2 MB/sec. Even though the data bus can go up to 40 MB/sec or higher, the actual mechanical head of the disk drive can only yield the average access time of 8 ms as of today, which means, if dealing with a non-contiguous byte-stream, it retrieves every single byte at 0.008 sec (125 bytes/sec). Therefore, no matter how fast the hard disk can be improved, it is still a mechanical part and a limitation is inherent.
Data bases are usually stored on the hard disk subsystem that consists of hard disk drives or hard disk arrays. Multimedia data bases, such as MPEG-II based data bases, have to constantly sustain each concurrent sharing at least 500 KB/sec. If the data to be retrieved are on one hard disk, then the hard disk at 2 MB/sec random seek throughput can theoretically sustain only 4 concurrent on-demand "sharings" on a multi-tasking server system. Still, the data have not yet been downloaded onto the client computers.
Though the hard disk array can increase the throughput, it still consists of a series of hard disk drives, which are mechanical parts. The increased throughput of a hard disk array when compared to the hard disk drive is nominal, but the cost increases tremendously.
When the client computer demands multimedia data from the LAN server's data base, the LAN server must:
1) retrieve the data from the connected hard disks and temporarily store the data onto its random-access memory (RAM); PA0 2) download the data from its RAM to the client computer. PA0 (1) By using more application-oriented LAN servers, such as media server, video server and CD-ROM server, PA0 (2) by defining a new network protocol called "isochronous" to warrant the minimum throughput to the multimedia-based nodes, so that the client computer in each node will not generate distorted video, PA0 (3) by using the intelligent hub/bridge/router to regulate the internal and external network traffic on different cable segments, PA0 (4) by using a more advanced video-compression method to deliver digital multimedia, PA0 (5) by using a more powerful processor-chip to develop the client-computer used as a set-top-box. PA0 a) The direct-access workgroup server can be directly accessed by all the connected Channel-processors on an internal workgroup server link, guaranteeing the multiple concurrent multimedia on-demand sharing. PA0 b) The intensive multimedia on-demand sharing, which is done within the workgroup on the internal workgroup server link, does not adversely affect the general network traffic, making the existing network link reliable, manageable and still usable for multimedia purposes. PA0 c) It eliminates the need for an additional system running a network operating system to perform as a workgroup server. This server system would have to be connected to all the workgrouped Channel-processors either through the existing network link, which actually adversely affects the network traffic, or through a new workgroup link, which needs additional linking-interface cards and yields only half of the performance when compared to the direct-access workgroup server PA0 (1) By using the analog carrier, such as RF CATV cable or RF microwave; PA0 (2) by using the digital carrier, such as Ethernet, fiber optic ATM (Asynchronous Transfer Mode) or cable modem. PA0 1) A series of input control ports for input devices, such as a keyboard port for PC-based keyboard and gamepad, a serial port for mouse and a scanner and a card-reader, and a game port for gamegear. All these input devices can be either wired or wireless; PA0 2) an addressable control/communication port that connects to the host iTVstation's Channel-processor using an internal control link. Some of the implementation examples for establishing the internal control link can be illustrated as follows: PA0 3) A video input port receives the video signal generated from any of the interactive TV channels through an internal video link. Some of the implementation examples for establishing the internal video link can be illustrated as follows: PA0 4) An audio/video output port to the attached display device, such as an NTSC/PAL port to connect to a television or to a LAN-node computer with NTSC/PAL video-capture capability. The iTVpanel is equipped with the capability of converting either the digital or the analog video into an NTSC/PAL video signal; PA0 5) an optional NTSC/PAL video bypass port for channeling other video signal source through, so that the non-interactive "public-viewing channels", such as CATV channels or other Pay-per-view channels, are able to broadcast to the iTVpanel users; PA0 6) an optional remote control interface port that receives the signal generated from the TV remote control; PA0 7) a series of optional data/communication ports to the external devices, such as a TV, a digital TV, a digital video disk, or a computer using interfaces, such as SCSI, Parallel port and Universal Serial Bus (IEEE, 1394); PA0 8) an optional system-exchange panel switch for hooking up with the LAN-node computer's input devices to control both the computer and the iTVpanel. When the switch is activated, those input devices, such as keyboard, mouse and gamepad, will directly interface with the iTVpanel. When the switch is de-activated, those input devices will control the computer. PA0 1) The Channel-processor that creates the private-viewing interactive TV channel, or the TeamPro iTVstation that is equipped with 4 Channel-processors and creates 4 private-viewing interactive TV channels; PA0 2) the direct-access workgroup server that provides the on-demand multimedia data base for all of the workgrouped Channel-processors or for a TeamPro iTVstation; PA0 3) the iTVserver that is an iTV-application-based LAN server and that creates a group-viewing interactive TV channel; PA0 4) the LAN server that provides data base services for all the Channel-processors and iTV servers; PA0 5) The iTVpanel that is either a PC-based or a microcontroller-based set-top-box and that interfaces with its host Channel-processor via the attached input devices. PA0 1) The internal workgroup server link that connects between the direct-access workgroup server and all of the workgrouped Channel-processors or a TeamPro iTVstation for workgroup server accessibility; PA0 2) the internal workgroup connectivity link that connects all the Channel-processors either in a workgroup or in a particular iTVstation for within-the-workgroup peer-to-peer connectivity; PA0 3) the internal network link that connects all the Channel-processors, iTVservers and the LAN servers for LAN connectivity; PA0 4) the internal control link that connects between the user's iTVpanel and its host Channel-processor for user interactivity; PA0 5) the internal video link that connects all the Channel-processors, iTVservers and all the iTVpanels for video delivery. PA0 (1) The unstable on-demand multimedia LAN servers; PA0 (2) the unregulated traffic on the already-congested internal network link; and PA0 (3) the deficiency of the "two-layer, single-link client-server network architecture using only two building blocks, i.e. the client computers and the LAN servers, on a single internal network link.
The LAN server incurs a lot of overhead when executing the downloading. How severe the overhead is depends on how many client computers are connected to the LAN server. That is the reason why a LAN server that handles the multimedia data transfer from the internal hard disk to the client computer can only sustain less than the theoretical number of concurrent multimedia on-demand sharing, which is four as described above. As a matter of fact, the Novell or the WINDOWS-NT LAN server can only sustain the concurrent multimedia on-demand sharing for two client computers.
Thus, the LAN servers, such as Novell-based or WINDOWS-NT-based are not powerful enough to be on-demand multimedia servers. They can provide only the concurrent multimedia on-demand sharing for two client computers as described above. It is impossible for these kinds of LAN servers to provide the multimedia on-demand sharing for all the connected client computers on a LAN. Even using a more powerful mainframe or a mini-computer as the central multimedia LAN server, the multimedia data base still has to be stored on the hard disk array, which is mechanically constrained to yield only a limited number of the concurrent multimedia on-demand "sharings".
It can be very inefficient and costly to provide a greater number of multimedia on-demand "sharings" by increasing the number of disk arrays attached to the central multimedia LAN server. If by so doing, it will only aggravate the server structure by adding more front-end processors, generate a lot of control/management overhead, worsen the internal data communication, complicate the data base management, and stretch the server to extremes until it is too big to handle and can no longer be expanded at all. This approach is of little value and economically unjustifiable. At present, a lot of these kinds of iTV installation have been proven too costly and still can not provide viable iTV services, mostly due to the fact that the on-demand multimedia LAN servers are simply not technically-feasible if based only on current hard disk technology.
The sequential read/write on a disk drive, which is another data-access method, has better throughput performance than that of the random seek. But, the random seek throughput is more useful because the user can interactively make on-demand inquiries from the client computer, creating the unpredictable data streams, which are totally different from those of a sequential read/write.
The sequential read/write can be useful in providing the video-on-demand, because except for the initial interactivity, most of the time the multimedia data streams are predictable. Video servers, as one kind of LAN servers, are built and operated based on this scenario and they can sustain up to 5 users using video-on-demand service concurrently from one hard disk. By using SCSI to link up a number of disk drives or disk arrays, the video server on a LAN can provide the service to more users at the same time. However, video servers are not ideal to provide highly interactive on-demand services, such as game-on-demand and shopping-on-demand.
Thus, it is not feasible to construct an on-demand multimedia LAN server based on the current hard disk technology. Also, the interactive multimedia/TV service based on the "two-layer single-link" client-server architecture is not going to work seamlessly. Although, the client-server network architecture is capable of delivering the text-based file-server service to all the client computers on a good-sized LAN, it can not overcome its inherent architectural deficiency when dealing with the interactive multimedia. Currently, there are some measures to improve the performance for delivering the interactive multimedia on the existing client-server network. They are:
But none of the above resolves the fundamental deficiency of the existing "two-layer, single-link" client-server network architecture in delivering the interactive multimedia.